1. Field of the Invention
The invention relates to a gripping head of an hydraulic sheet stretcher of welded design, comprising a horizontal cross member and a series of vertical laminae welded thereto which form the gripping aperture of the gripping head.
2. Description of the Prior Art
As the thickness of the sheet to be stretched increases, the stresses in the gripping aperture, in which clamping jaws for holding the sheet to be stretched are disposed, become increasingly high, relative to the width of the sheet. This has led to the gripping aperture advantageously being made up of laminae of sheet metal. In addition, the entire gripping head represents a heavily loaded transverse beam which comprises a correspondingly constructed cross member.
The known manner of securing the laminae of the gripping aperture to the cross member is by inserting the laminae into the comb-like upper and lower flange of the cross member of the respective gripping head and by welding them together by fillet welds. In this comb-like design these fillet welds have a high stress concentration factor K.sub.t and are in the range of maximum tensile and bending stresses. Furthermore, these weld seams must be welded by hand. In order to be inserted into the comb-like flanges the laminae must be reduced in thickness at their ends.